Transmission characteristic correction



Dec. 3, 1946. T. SLONCZEWSKI 2,411,903

TRANSMISSION CHARACTERISTIC CORRECTION Filed March 13, 1943 FIG 4 I 'REOUENCY vvvvv VOLTAGE m ,muanosau "l- OUTPUT ATTO EV Patented Dec. 3, 1946 UN [TED S PATENT OFFICE f2,411,9,o3 mauslvnssronionaaac'rimrs rrc I OORREGTION 'i'haddeus Siiof Gienwood Landing, N. Y., assighor to" ell Telephone Laboratories,. incor- 'poraited, New York, Y., a corporation of New York Application March 13, 1943, Serial No. 479,146

This invention relates to electric wave transmission circuits and more particularly to the adjustment, correction or compensation oi the level transmission characteristic, for example, the

voltage input-output characteristic of. a circuit,

portions from that needed to meet specific transmission requirements. The requisite equalization could be obtained by associating with or includin one or moreof thea npliflers oi the circiiit /suitably designed equalizers .or amplifier interstage networks. Suchl equalizers or networks, however. maybe quite-complex, and dim- 'cult to design and construct; a It is an object of this ihv'ent'iomto. adiust, correct or compensate'the level transmission characterlstic, forexample, the voltage: inp'uhoutput characteristic of an amplifier in a .relativ ely simple manner. 1

1h accordance with a specific embodiment of the invention disclosed herein; the level transmission characteristic of a circuit is adjusted or corrected. in preassigned respects'by translating a portion of the variable amplitude input to the circuit into direct current potehtials, generating under control of said pot'ent'iai's'jjla constant amplitude, variable Irequency. wave having a linear frequency-control potential characteristic, modifying the generated wave by transmitting it through an equalizerhav-i'ng ,the required lossire'quency characteristic, translating the modihed wave into direct current potentials and inipressing the latter on the input of the circuit for gain control action.

A more complete understanding oi the invention will be obtained from the detailed description that follows taken in conjunction with the showing of the appended drawing whereinz.

Fig. 1 illustrates a circuit arrangement emb'odying the invention; and

Figs. 2, 3 and 4 show curves to be referred to in explaining the principle of the invention.

With reference to the drawing, the invention is illustrated as applied to the correction or adjustment of the input-output or voltage transmission characteristic of a transmission circuit comprising an amplifier. The amplifier may comprise a vacuum tube or electronic device Ill whose input gridcathode circuit may be connected to input terminals ll, ll through a coupling condenser l2. and whose cathode-anode circuit may he resistance-capacity coupled, for example, to a succeeding amplifier stage (not shown), or other circuit components included generally by the designation output The input to the ampllfier may comprise a variable amplitude signal wave. The amplifier may have a voltage inputoutput characteristic illustrated generally by the ill I curve of Fig; 2.

8 Claims. (Cl. 178-44.)

Fo eq eos s f t a ticu a itlu i the mpli ie & cluded, it may bedesired or consideredlreguisite .that. the, inputout ut characteristic should actually coniornptothat, illustrated by. the curve A'B'C'D-C The adjustment or eorre ctiqn--.-re-

quired is provided by the control circuit, iconnectedIacross the input to the amplifier This control circuit may comprise a detector [5 coupled to a frequency modulator iiiof-jhe well-known reactance tube type for regulating the constant amplitude frequency outp itioi an oscillator n. Theiatter is coupled to fler 48, whose output is in turncoupled tomn equalizer I! of suitable loss-frequency characteristic. The equalizer output is connectedthrbugh a rectifier 20, tothelinputIgrid-cathode}circuit of the amplifier on the grid'side dllthefco ipli lng cotidenser.l2.. The const'a'iits" oi the-frequency modulat'or-goscillator ctr-cult. would be chosen so that the; output frequency 01 the oscillator bears a substantially linear relation to the input voltage of the modulator as illustrated 'byfthe curve at Fig, 3. 'i he design oi theequali'zer would be such, that thecon'stant amplitude. niry'ijiig frequency wave input thereto will be attenuated such thiit the attenuated OSCiIIalJMIiSQY 'B Q 'in amplitude in correspondence to the vane-tug? r qulredtoflbe lhtroduced in the normal 1 pa,- oui u ha c r tic o the mp fier; that 13's. the characteristic per curve" oi Elli-$3111 order to modify it to the desiredfcharacteri'stip, that is, the 'ciiaracteristit b curgen aicpr ,9: Fig. 2. File. 4 iliustiates th'el'oss irejqueilcy jcn, 1i;- acteristic that the equalizer would haveto, enfa 1e obtaining the modified characteristic A'B'C'D" of Fig. 2. The points A", B", C", D" on the curve of Fig. 4 corresponds to points A. B, $3.131 on the curve inFl'g. 2. t In operation, a portion oi the variable amplitude input wave to the amplifierlil is detected in the detector l5 and translated into direct current potentials corresponding to the instantaneous amplitude of the input wave These potentials are applied to the grid electrode of the reactance-tube modulator IE to vary theefi'ective reactance thereof and, consequently, that of, the irequencydetermining circuit 21 of the oscilla tor. The oscillations generated by the oscillator will vary substantially linearly with the variations in the input potential to the modulator, and wiil be of constant amplitude, The output of the oscillator may be amplified to the desired or necessary level by the amplifier stage IB, and then applied to the equalizer to be attenuated in accordance with a los3-ircquency characteristic determined by the desired modification in the input-output characteristic under adjustment or correction. The attenuated oscillations are translated by the rectifier into direct current potentials andare applied to the grid-cathode circuit ,gf the' amplifier to adjust the gain of the amplifier in positive or negative direction with variation in the amplitude of the input wave thereby introducing the correction required to provide the output corresponding tothat required in accordance with the desired input-output characteristic.

Although the inventionis disclosed with reference to a single embodiment .ther eoi it will be understood that it is not limited thereto but is of a scope evidenced by the appended claims.

What is claimed is:

1. The method of correcting the input-output characteristic of a, circuit that comprises translating a portion of the variable amplitude input the circuit into control potentials, generating constant amplitude oscillations varyin fl nearly in ireduency with respect to said potentials, attenuating the oscillations in accordance with a lossf'requency characteristic related to the desired deviations in the normal input-output characterl'stic, and translating said attenuated oscillations into control potentials for application to the input of said circuit,

' 2. The method of correcting the input-output characteristic of a circuit that comprises translating a portion of the variable amplitude input h ircuit into direct current control potenthi imp es constant ampli ude i lat o va 'ance with aloss-frequency characteristic related 59 the d sire evia ions n the no mal np e ieilt e erav r si a a ran in sa d at gated oscillations into direct current control poteritials for application to the input of said circuit for gain control purposes.

3 in combination, a, wave transmission circuit having normally a particular input-output characteristic and means to modify said characteristic in desired respects, said means comprising means to derive from the input wave to said circuit potestic e mrre con in to the aryin pl ude 9! said wave, means responsive to said potentials to generate constant amplitude oscillations varyng' in frequency linearly with respect to said potential s, means for attenuating said oscillations the attenuated oscillations vary in amfllirii l ilit' pitude related to the deviations required to be introduced in the normal input-output characterlstlc to, modify it to the desired characteristic, and means for deriving potentials corresponding to the varying amplitude of said attenuated oscillatigns and for applying said potentials to the input of. an i i Q. In combination, a wave transmission circuit having normally a particular input-output characteristic and means to modify said characteristic in desired respect, said means comprising a rectifier for deriving from the input wave to the circuit direct current potentials corresponding to the varying amplitude of said wave, a reactancc-tubc modulator-oscillator responsive to said potentials to generate a constant amplitude, variable frequency output varying in frequency linearly with respect to said potentials, means for modifying the oscillator output in accordance with a loss frequency characteristic related to the desired modification in said normal input-output charactcristic, and a rectifier for deriving direct current potentials corresponding: to the varying am plitude of the modified oscillator output for up plication to the input of said circuit,

Q. In combination, a wave transmission circuit including an amplifier having a particular inputz ieesrlri ue y wi h s e t to sai .pgisl ia att nu n the c a ons in acco doutput characteristic and means-t {correct said characteristic in desired respedts, said means pomprising means for translating 0. portion of a variable amplitude wave input to the amplifier into -a constant amplitude, variable frequency wave, means for translating said latter wave into a wave varying in amplitude related to the desired correction said input-output character- 151210, and means for converting the amplitude variable frequency wave into direct current potentials for application to the input of said amplifier.

6. ;In combination. an amplifier having a particular input-output characteristic, an input circuit and an output circuit for said amplifier, a source of variable amplitude electric wave to be applied to said input circuit, and gain control means to vary the gain of the amplifier in response to the wave input thereto to modify said input-output characteristic in preassigned respects, said means comprising a circuit for translating a portion of the wave input to the amplifier into a constant amplitude variable frequency wave, the frequency of which varies with variation in and in direct proportion to the amplitude of the input wave, and means for attenuating said variable frequency wave so that the wave has an amplitude-frequency characteristic corresponding in outline to that of the desired oorrested input-output characteristic, and for translating the attenuated wave into potentials for application to the input-circuit of the amplifier'in a sense to produce gain changes in the amplifier effecting preassigned deviations from the normal input-output characteristic of ,the i implifier.

I. In combination, an amplifier "havingja particular input-output characteristic, an'input circult and an output circuit, a source of variable amplitude electric wave to be applied to saidinput circuit, and gain control means for said amplifier to vary the gain of the latter in response to a function of the input wave to modify said inputut ut a c s i n un s g d respects. said means comprising means to derive direct current potentials from a portion of the input wave, means responsive to said potentials to generate a constant amplitude, variable frequency wave the frequency of which varies in direct proportlon to the magnitude of said potentials, means to vary the amplitude of said variable frequency wave as a function of the gain correction required to modify said input-output characterlstic in the desired respects, and means to derive direct current potentials from said variable 'amplitude, variable frequency wave for application to the input circuit of said amplifier.

8. In combination, a wave transmission circuit having normally a particular input-output characteristic, and means to modify said characteristic in preassigned respects, said means comprising means to derive from the input wave to the circuit direct current potentials corresponding to the varying amplitude of said wave, oscillation generating means responsive to said potentials to generate constant amplitude oscillations varying in frequency linearly with respect to said potentials. means for attenuating the oscillations such that the attenuated oscillations vary in amplitude in correspondence to the desired deviations from said particular input-output characteristic, and means for deriving direct current potentials corresponding to the varying amplitude of said attenuated oscillations and for applying said secondmentioned potentials to the input of said circuit,

THADDEUS SLONCZEWSKI. 

